Copper recovery



United States Patent 3,480,477 COPPER RECOVERY Allan F. Levin, Doylestown, Pa., assignor to Metal Wire Recovery Corporation, a corporation of the Commonwealth of Pennsylvania No Drawing. Filed May 19, 1967, Ser. No. 639,614

Int. Cl. B08b 3/10 U.S. Cl. 134-45 4 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention This invention relates to one step in a general process relating to the recovery of electrolytic grade copper from scrap, more particularly from scrapped runs of substandard insulated wire production. The wire is chopped, and then air separated to remove small fragmented bits of insulation with some small content of copper. This air separated fraction is further treated by other means. The non-air separated portion is then treated in an autoclave, the treatment in which is the most important part of the present invention. After the autoclave step, the material is permitted to drip, it is then treated in a hammermill to break off carbonized insulation, is then vibrated on a screen and washed with detergent, then re-subjected to a hammer mill step, then to a water rinse, then a rotary dryer, and then may be further hammermilled, subjected to magnetic separation and another air separation.

Description of the prior art Some earlier United States patents disclose related subject matter which deals in a broad way with the present invention, but which does not disclose the particular detailed improvements which result in the improved present process. Such early United States patents include Patents 1,185,641; 1,842,970; 3,010,852; 1,726,623; 2,077,785; and 2,541,703.

SUMMARY The critical aspects of the invention relate to the conditions and the steps in the autoclave and to the steps directly associated with the autoclave step. The invention permits the production of very high grade copper from insulated wire scrap. Such recoveries have been attempted with tin, solder, and insulating materials particularly including polyvinyl chloride. Other aims and objects of this invention are further understood in connection with the following specification and claims.

Important points in this invention relate to the chopping of the wire into certain lengths, and into the conditions in the autoclave. The chopped wire is subjected to oil whose hydrocarbon composition shows an aromatic ring percentage of at least ten percent and a paraffin chain percentage of less than fifty percent. The oil temperature is between 450500 F. and is circulated. A chopped length size of the Wire is approximately between one quarter and one half inch. The amount of polyethylene in the chopped insulated wire which goes into the autoclave must be less than two (2%) percent of the total weight. The amount of polyvinyl chloride in the chopped insulated wire that goes into the autoclave must be at least five (5%) percent of the total weight. If there is not sufficient polyvinyl chloride in the chopped material fed to the autoclave, additional polyvinyl chloride is added before the cooking step. A cold oil flush to prevent flash fires is applied before opening the autoclave. The time in the autoclave is between one and three hours. Non-copper material remaining after removal from the autoclave is of a type that is brittle and nonadherent, and is removed by a succession of physical scrubbing and breaking steps, such as hammermilling, vibrating, and air separation, as well as washing, degreasing, and rinsing. For the purposes of this invention, the steps of removing the brittle material after the autoclave step may together he considered as mechanical separation.

DESCRIPTION OF THE PREFERRED EMBODIMENT The wire as received for the processing of this invention is copper. It contains quantities of solder, and quantities of tin on its surface at various points. The insulation may vary. Such insulating material normally is primarily polyvinyl chloride in the present process. Other insulating materials may also be present. Such materials include rubber, nylon, Teflon, fabric, and paper. For this invention, only a certain maximum amount of polyethylene may be included in the insulated material, measured as a percentage of the total weight of chopped insulated wire going into the autoclave.

The wire is chopped and sieved so that at least the great majority of the cut pieces have a length of between one quarter inch and one half inch. The exact percentage of pieces of this length is not in itself of a critical nature, but it can be stated that almost all of the chopped lengths should be of no more than one half inch length.

The chopped material is placed in baskets in a sealed autoclave. It has been found that if the wire was simply coiled in the baskets, there was not enough oi] penetration to properly treat all the insulation, and the process was not successful. It has been found that an air separation step is preferable after the chopping step. The air separation, taking place in a standard air separater, removes much of the lighter plastic materials. The critical point is that the material going into the autoclave should consist of no more than approximately ten (10%) percent plastic. If there is a higher percentage of plastic than this, it has been found that there is also insutficient oil contact due to the tacking effect of the plastic. Thus, limitations on the material going into the autoclave include half inch maximum length and no more than approximately ten (10%) percent of plastic material.

Other limitations on the material going into the auto clave relate to the type and percentage of the plastic.

The percentage of plastic to come within the limitations of this invention are as follows. It has been found that there must be no more than two (2%) percent of polyethylene, measured as a percentage of polyethylene to the total weight of material going into the autoclave. Greater percentages of polyethylene than this cause a rapid failure of the process. This is because the presence of the polyethylene tends to make the oil jell. The less polyethylene present below this limit, the greater the desirability. That is, as there is lower and lower percentage of polyethylene, the hot oil may be recirculated longer and longer before it has to be replaced.

Another limitation concerning materials is that it must be at least a minimum amount of polyvinyl chloride in the material going into the autoclave, on the basis of percentage of polyvinyl chloride of total material into the autoclave. It has been found that there must be at least five (5%) percent polyvinyl chloride (PVC). Experiments so far have indicated that if no PVC, or less than the required amount of PVC is present, as stated, the amount of removal or embrittling of the insulation on the metal is very much less for a given time and temperature exposure in the autoclave than otherwise.

It has been found that if the chopped material as it comes from the chopper or the air separater does not have at least this minimum percentage of PVC, small fragments of PVC may be added before the hot oil treatment is started. It has been found that while five (5%) percent is considered a suitable minimum, it has been found that if all the insulation associated with the metal of the chopped wire is PVC, that is, the total percentage of PVC to total weight is approximately ten percent, this is a desirable and preferable condition.

The exact reason for the great desirability of the PVC is not completely understood. It is thought however that there are several factors. There is a creation of hydrochloric acid during the cooking step. It is believed that this hydrochloric acid is important in the process, par ticularly in the creation of lead and tin salts from the solder and tin associated with the wire. There is also believed to be an exothermic reaction due to the presence of the PVC which induces additional local heating where it is most desirable, that is, immediately adjacent the surface of the metal.

The autoclave is closed, and oil between the temperature of 450500 F. circulates continually through the baskets of chopped wire. The circulation is important in flushing away the materials to be removed from the copper. It has been found that below approximately 450 F, the process will not Work regardless of time in the bath. The upper limit is primarily a function of flash point and decomposition point of the oil. Some suitable oils have flash points higher than 500 F., but flash fires have been known to result even below the given flash point. It has been found that the contents of the autoclave should be cooled to no more than 200 F. before opening the autoclave to avoid the possibility of flash fires, even though this is well below the flash points of the oils. The reason for this flashing below the expected flash point is not completely understood. Therefore, for

the purpose of safety, a cold oil flush is performed before the autoclave is opened, and the temperature is thereby reduced to no higher than approximately 200 F. The upper given limit of 500 F. is not exactly critical, but is simply a preferred approximate upper limit, and the problems of decomposition and flash, as well as the economic problem of having to cool the oil further before opening the autoclave governs this limit. Furthermore, going above 500 F. has not been found to produce significantly faster results to offset the other disadvantages described.

In the oil used, in a carbon type analysis of the hydrocarbon composition, the percentage of carbons in aromatic rings should be at least ten (10%) percent, and the percentage of carbons in paraffin chains should be no more than fifty (50%) percent. These conditions of oil composition may be considered to describe an oil of relatively high aromatic content and relatively low paraflinic content. If the oil has a reversal of. these characteristics, that is, if the percentage limitations are exceeded, it has been found that there is a tendency to clog the process, because more sludge is formed. The number of times that the oil can be recirculated is thus lower, and there is also more equipment corrosion.

Suitable oils include oils marketed under the known trademark and trade designation of Sun Oil 310 and Sun Oil Circo Light. These oils may be further identified as petroleum distillate products having the following characteristics.

Viscosity, BUS at F. lll] All Gravity at tit) F .r 30,1 Flush Point. F 350 Pour Point, O F -45 Aniline Point, 1" 156 Viscosity-Gravity Constant 886 0. 863 Hydrocarbon Composition:

Percent G, {Aromatic Rings) 10 16 Percent. C (Naphtheue Rings) 4t] 43 Percent C ttaralllu Ch tltlS) 4 41 The minimum temperature of 450 F. is not high enough to melt pure tin, although it is close to the melting point of solder. Neverthless, the tin and solder do come oil the copper in the cooking bath. These metals appear in the oil bath as stannous and lead salts. This is an exothermic reaction, and the additional reduction of heat locally at the surface of the copper increases the efliciency of the over all operation. Other chemicals are also produced during the cooking step.

The oil recirculated during the cooking step is reused. A storage and settling tank of conventional construction are provided. The sludges resulting from the cooking step settle out in the settling tank. The oil going into the autoclave is heated in a heat exchanger. Some makeup oil is of course added from time to time. Gases produced during the cooking step are vented off.

After the cold oil flush to reduce the temperature of the autoclave to approximately 250 F. or less, the baskets of chopped wire are removed and drained. It is found that any material remaining on the copper is of a brittle nature which is relatively easily removed by what is here termed mechanical separation steps. The type and amount of these steps may vary. Typically, the drained material is passed through a hammermill, a vibrating conveyor where it is washed with a caustic detergent and degreaser such as is sold under the trademark Crystal Soap by Wyandotte Chemicals, anohcr hammermill, a water rinse and a vibrating pan, a rotary dryer, another hammermill, a magnetic separation step, and another air separation step. The last three steps have been found o be useful sometimes "insurance? and other times are not essential. Solvent degreasing processes, using trichlorethylene for example may be substituted for the detergent washing and other rinsing and drying steps.

The time in the autoclave must be at least one and one half hours, and it has not been found necessary to exceed three hours. A preferred time in the limits of temperatures and oils as disclosed has been found to be ab ut two hours.

The use of nonoxidizing gaseous atmospheres, and of other liquid mediums such as water have not been found 5 6 to produce as satisfactory results as are obtained by this 3. A method of recovering copper from insulated copinvention. This present invention produces its results per wire, wherein said insulation includes at least one of without air pollution, without further refining of the polyethylene, polyvinylchloi'ide, textile, and said wire has copper before it may be used, and with a minimum of ailixed to it at least one of tin and solder, comprising skilled labor. (a) chopping said wire into lengths of no more than Examples of various runs are given below. one half inch,

Wire to Autoclave Percent Percent Percent Sir ll) (including Percent Percent after after added Auto- Sn b ineeliaiiniecliaiimats, Oil clave after after ical icul Percent Percent all Wire insulation temp, time, I autoauto scpnra separuinsulation PE apprx.) type F. hrs. Oil type clave clave ti'oii tion 10.0 lVC,PE,textile 500 l SuiiCirco Light ,l 025 0(i3 2.4 0 PVC, textile 450 2 .....d0 .070 .0045 ,iiii .025 12.0 0 9 o 4 H 2 un 310 .027 .0007 .010 .0035 2.1 0 5 Pvo"... 450 .c do .i .080 .0042 .012 .0013 5 ApX.1 7 PVQPE 500 2 Sunfiuudvx .025 .003 7 Apx.2 7 PU\",PE. 500 2.5 SlliiSundex l7 0.25 .Uti3 8.5 Apinli 7 IVQPE.-. 475 3 SunUircoLight .025 .i)ii3 In the above chart, the legend PE indicates polyethyl- (b) air separating lighter portions from said chopped me The wire in each run was copper wire with the wire, amounts of tin and solder normally associated with com- (c) adding as much polyvinylchloride as necessary to mercial communications wire. The oil temperatures and bring the percentage of polyvinylchloride in said times are approximate. In the column headed Wire chopped insulated wire to at least 5%, type, the insulation materials only are given. Where (d) providing said chopped insulated wire in an autoa space is not filled in, data was not available. In each clave said chopped insulated wire having no more case, the material out of the autoclave was associated than 2% polyethylene, with an imbrittled hard black material which was easily (e) circulating petroleum distillate oil through said removable by the mechanical separation steps. In all chopped insulated wire for a period of time of more runs, the average ratio of input chopper wire to oil was than one hour, at a temperature of at least 450 F., approximately 138 pgundg per fl n, I ll r the 25 said oil having at least 10% carbon and aromatic chopped lengths were between one quarter and one half rings and no more than 50% carbons and araffiri i h. chains,

The scope of this invention is to be determined by the q g 9 in a d autoclave to below the flash following claims, and is not to be limited by the foreml f aid oil, going description which is illustrative. (g) Plachamcally SePfimImg from 531d PPtE th em- I claim: brittled material mixed therewith. 1 A method f recovering copper fr i l t d 4. A method as set forth in claim 3 wherein said oil copper Wire, comprising temperature is between 450500 F., the time of said cir- (a) providing in an autoclave insulated copper i i ciilation is between one and three hours, after said circulalcngths f no more than h ]f inch, d h i tion the oil is cooled to a temperature no higher than apno more than approximately 15 percent insulation, p ma ely 250 F. no more than approximately 2 percent polyethylene and at least approximately 5 percent polyvinylchlo- References Cited (bride, l 1 d n 1 h h d UNITED STATES PATENTS circu ating petro eurn isti ate oi t roug sai g autoclave, said oil having at least 10 percent carbons 3 555 134,449 in aromatic rings, and no more than percent car- 2'417468 3/1947 Canziani g g 38 2 bons in paraffin chains, said oil being at a tempera- 2563417 8/1951 Pessel 134:38 XR ture of at least 450' F., and at the time of said cir- 27O9'666 5/1955 S g XR culation being at least one hour, 2891881 6/1959 jgffe XR (c) cooling oil in said autoclave to below the flash 3:225:428 12/1965 Dem 29 403 point of said oil, ((1) mechanically separating from said copper the em MORRIS O WOLK brittled material mixed therewith. 2. A method as set forth in claim 1 wherein the tem- 0 MILLMAN, Assistant Examiner perature of said oil is between 450500 F., the time of said circulation is between one and three hours, and said CL oil is cooled after said circulation to a temperature 29-403; 134-2, 6,19, 38 higher than approximately 250 F.

Primary Examiner 

